Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/127383
o wn long-stroke versio n of th e 8-valve Du cati mot o r, in wha t is essent ia lly a d evelopm en t exe rc ise th at ha s th e u seful add it io na l benefit of yield ing wort h wh ile publicity returns - especia lly when th ey get in th e p oints, a s th ey did a t bo th th e fir st two rounds, co u rte sy o f guest riders Steve Man ley an d Do min ique Sarron, recrui ting o n a race by race basis after wor ks rid er Vittorio Sca to la high-sided h im self into hospi ta l wi th a bad ly broken leg i n th e fi rs t pra c t ice sess io n a t Don ing ton . Birn ot a h as extensivel y revamp ed the Duca ti eng ine , wh ich n ow mea Stires 95x68 mm in Tesi Superb ike form , fo r a cap ac ity of 964cc, a n d delivers 128 bhp a t th e rear wheel, a t 10,000 rp m - a goo d wa y fu rther do wn the rev sca le th an the shor ter-stro ke (64m m) Du catis - as well as o ffer in g a mu ch meati er midran ge a nd bott om en d pow er cu rve. T oo mea ty, perh a p s, fo r keep in g th e front wheel dow n exiting slow tu rn s is a m ajor headach e, as Steve Manley fou nd in th e first race at Doning ton , when em bro iled in a d ice w it h Fa la p p a o n t h e seco nd factor y Du ke. Steve took a big h andfu l o u t o f th e ch ica ne a fter usi ng the T esi's undou bt ed b raki ng a bi lities to sit it o u t succ essfu ly with the Ita lian hard man , o n ly to ha ve the fro nt wheel co me u p so fa r in the a ir, it al mo st fl ip ped hi m o ff backwards! Then, when th e wheel to uched dow n aga in with a ba ng , it di d so so hard, it dented the fro nt ri m ! T he p rob lem is exace rba ted by th e Iork less T esi chass is' rear ward s weig h t b ias - n ot helped by the siting o f th e EF I/ems co nt ro l box in th e tai l - of 49 / 50 %, At 336 lb. ha lf-d ry, th e Tes i toda y is a t the sa me stage th e wo rk s The Tesi is most noted for its fo rkl ess front suspension and hub-center steering. The major proble m at this p oint seems to be one of aerodynam ics an d stabil ity . Du ca ti was a yea r ago , but a s ch ief eng ineer P ierl ui gi Marco n i says, the b ike is ba sica ll y o verd ime ns io ne d , since they had no real idea ho w stro ng th e va rious co m po nents n eeded to be for long-term life in su ch a revol u tion ary design , so erre d o n the safe side. Even so, Sarr o n felt the front swinga n n wa s flexing a fter ear ly tests, lead in g the tea m to fro nt at J arama with each o f the tw o bikes (o n ly thr ee racin g T esi s ha ve been bu ilt so far ou t o f th e p rojected five) with un pr ett y g ussets a n d str u ts un d er th e sw in ga r m . Fra nk ly, it's u n likel y there's a ny flex there, since th e dimen sio ns a re th e sa ult' as the rear swin ga rm . wh ich a bsor bs a ll the side -loading o f th e cha in p u ll q u ite h app ily . , . ! After in it ia ll y em p loy ing sus pe n s io n un it s fro m th e ir tr a d i ti on a l s u p p l ie r Ma rzo cch i. Bim o ta h a s become d isencha n ted with th e effo rts o f the Ital ian suspen sion ma nu facturer a nd eq u ip pe d th e T esi racer with O h lin s u n its fro n t a nd rear. Even th ese aren 't per fect, beca use th ey're design ed for the rea r end o f a co n vent io na l bi ke a nd have th e wron g kind o f valving for a hu b-cen ter machin e, but new , specia lly -made un its are o n th e wa y, a nd will be tested in co nj uet io n with a sim i lia r set from Wh ite Po wer. Wh en t ha t ha p pen s, it ma y hel p reso lve the T esi's bi ggest prob le m tha t's sho wn u p so far , a lack of sta bi lity in a straigh t line that wa s very evide nt at j a rama , w here Sa rtou 's bike wa s wo bbling all the wa y dow n th e front stra ig h t, a fter h itt in g the bu m ps on th e exi t o f the fast swee per leadi ng o n to it , wh ich ba sica lly u nsett led th e bi ke a nd sen t il int o th e wea ve. T he prob lem ho wever is a lmost cert a in ly ae ro dy nam ic, beca use ha ving been design ed to loo k pr ett y ra th er than efficient , the T esi bod ywor k h as not yet seen the in side o f a wi nd tu n nel , a n d th e a ir is certa in ly ge tt in g under th e h igh -set, sq ua re nose, and ligh ten ing the fro n t en d so th a t, wh en the wheel h its a bu mp , it sen ds the bik e int o a speed wob ble. T ests at Mi sano with a wr a paround scree n a n d dro op-sn oot nose h ave shown a ma rk ed im p ro vem en t, bu t Bim ota a re stuck with the homo loga ted bod y sha pe for th e rest o f th is sea so n , till th e Milan Show when th ey'll launch th eir revam ped versio n in time to ho mol oga te it for next year. It 's a sh ame th a t th e aero dy na m ic problem shou ld h ave ar isen , beca u se it co m p ro m ises p eopl e's per cep tion o f th e h u b-cent er T esi chassis' Iork less fro nt suspen sio n a nd steering, So far , th is ha s more tha n li ved up to expecla tio ns in turns, th o ug h it tak es a co n scio us effort o n the part o f th e rider to leave hi s bra kin g as la te as th e c hass is w i ll le t yo u : Sa r ro n w a s not iceabl y rel ucta nt to test the b ike's pot enti al in th is regard a t J ar ama , co mplai n in g that th e steeri ng was too hea vy to lay it in to the turn on th e br ak es, Ma n ley had no su ch p ro b lems in ar clirna rivar io n at Don in gton , and j udging by hi s j ara ma per fo rm a nce o n h is agei n g , u nderfu nded p rivat ee r Ya maha , wo u ld have been a bet ter bet for Bim o ta to stay with th an a former (; 1' ride r perh aps too set in h is wa ys 10 adapt 10 th e T esi desig n , Sti ll. Bimo ta a re happy a t the progr ess mad e so far wi th suc h a new a nd a va n tga rde race r, a nd Mar con i is a lready app lying man v o f th e lesson s learn ed in SBK to h (s 500 G I' twin , wh ich a lso spo rts a Tesi chass is. f~ YAMAHA. Motorcycles with built-in' insurance, Sounds like apretty radical idea. Doesn't it? Well, it's real. Every 1991 street-legal motorcycle we sell comes with insurance built right in! All you have to do is grab the one that grabs you , show us your valid driver's license, and you 're fully covered * for ayear. Looking for the catch? Sorry, there isn't one. Considering the availability and cost of insurance, it's asmart idea. And ,with our financing program, owning aYamaha is easier than ever. So , get on the one motorcycle that's like no other in the world. Yamaha. A li(fft~YAMAHA ~~~~ ,. icense required. IInsurance P rogramisoptional and not available inall states.Askyour local dealer foravailability.